Old school supervised polarity reversing fire alarm notification circuit. Open circuit or field wiring with switch before last led on top right to trouble circuit at panel. Close switch on top left to reverse polarity on outgoing field wiring to turn output circuit on, lighting the field devices represented as led's which could be either strobe lights, horns, etc. LED's serve well for demo circuit because they are inherintly diodes but normal indicating appliances have diodes built into the unit itself in parallel with field wiring for reverse polarity activation. Hope someone might find these posts of interest. d...
Changed led's to conventional lamps and added diodes internal
to each field device to illustrate thier necessity for reverse polarity supervision. d...
